In connection with plants where such conveyor belts are employed, it is known that for various reasons the belts “wander” laterally on rollers and along their tracks. This is due in part to uneven loading, partly to misalignment of supports and rollers and often a combination of several different factors that produce a random pattern of movement for lateral movement of the belt. This lateral movement may be defined as a deviation from a basic neutral position where the belt travels in its longitudinal direction along an imaginary centre line or other kind of desired path over rollers or guides. Lateral movement in the belt will move the belt to the side of this neutral position or path for the belt, whereupon it should be restored to this neutral position. This creates the need for a guiding device that senses when the belt is out of the neutral position, whereupon it corrects the travel of the belt in its longitudinal direction, thus returning the belt to the neutral position. This may also be a dynamic correction device that constantly corrects the belt relative to positions on both sides of the neutral position as well as preferably in relation to both directions of travel in the belt's longitudinal direction.
A belt guidance unit for the above-mentioned tasks and areas of application ideally should furthermore be simple and robust to operate while it must be easy to install and adjust before use. The construction should furthermore be capable of being adapted to the existing conditions and loads either by employing different dimensions for the constructional parts or by being able to adjust the design of the constructional parts that are already installed in an existing system, such as, e.g., rollers, guides, mounting brackets, etc.
A belt guidance unit, moreover, may be able to be adapted for a conveyor belt that moves in one or two directions without major constructional alterations.
From previously known solutions within the field, a device may be mentioned for conveyor belts that travel over rollers or supports, described in DE 174 491, which device corrects for lateral displacements that occur in the belt during operation, causing the belt to be returned to its neutral position. A set of guide rollers for the conveyor belt is mounted on a plate, which is rotatably attached to the base. To the rotatable plate is mounted an arm with a tie bar. The arm may be articulated and rotatable about a pivot that is attached to the base. To the tie bar are attached guide rollers, which move along the edge of the conveyor belt and which, in the event of lateral displacement of the belt, transfer the movement to the tie bar. The movement is transferred to the lever arm, which in turn transfers the movement to the plate, thus causing the guide rollers' axes to be tilted and returning the conveyor belt to its neutral position.
The above-mentioned solutions, however, is relatively complicated in the mechanisms for producing movement and the solutions are therefore expensive and complicated with regard to mounting and adjustment, while also requiring some inspection. Due to the complicated solutions they are relatively specific for a particular size and type of conveyor belt. It may be difficult or not possible to alter the mechanisms for various sizes of conveyor belts.
It is therefore an object of the present invention to provide a guide device or a belt guidance unit that may be alter or adjusted for different types and ranges of conveyor belts.